1. Technical Field
The present invention relates to an organic electroluminescent (hereinafter, referred to as organic EL) device, a driving method thereof and an electronic apparatus.
2. Related Art
An organic EL device having an organic EL element as a self light emitting element that requires no backlight has been drawing attention recently. The organic EL element is composed of an organic EL layer, i.e. a light emitting element, disposed between a pair of electrodes opposed to each other. An organic EL device, on which a full-color display appears, is composed of the light emitting elements, each having a light emitting wave length region that corresponds to respective colors of red (R), green (G), and blue (B). When a voltage is applied between the pair of electrodes opposed to each other, injected electrons and holes are re-bonded in the light emitting element, thereby the light emitting element emits light. The light emitting element included in such organic EL device is typically formed of a thin film having a thickness of less than 1 μm. In addition, the organic EL device needs no backlights used in conventional liquid crystal display devices since the light emitting element emits light. Therefore, the organic EL device has an advantage in that it can be made extremely thin.
In the organic EL device, when white and any colors are displayed by combining light emitted from light emitting elements each of which emits respective colors of red (R), green (G), and blue (B), each light needs to be balanced in luminance in order to achieve white at an targeted coordinate point in the international commission on illumination (CIE) standard coordinate system. As a typical way to take the luminance balance, a method is exemplified in which a different voltage is applied to respective light emitting elements each of which emits red (R), green (G), and blue (B) for adjusting the luminance.
However, adjusting the light emission luminance of the light emitting elements each of which emits red (R), green (G), and blue (B) by applying a voltage causes a different injection current in each light emitting element depending on colors. Here, the light emission lifetime of the organic EL element largely depends on the injection current. Thus, the different injection current in the light emitting elements each of which emits the respective colors causes a different speed in luminance deterioration depending on colors, thereby resulting in the white balance being lowered with time. In order to solve the problems described above, a technique is disclosed in JP-A-10-39791. In the technique, the white balance is achieved by differentiating a light emitting area while the same voltage is applied to light-emitting elements each of which emits respective colors.
The use of the technique disclosed in JP-A-10-39791 allows the luminance balance of each color to be maintained for longer period as compared with the conventional one. The technique, however, has a drawback in that a difference in individual organic EL devices cannot be adjusted. In addition, it cannot cope with changes in light emitting characteristics with time, i.e. deterioration with time.